Ribbon rewinding apparatus especially for high speed printers

ABSTRACT

Ribbon rewinding apparatus includes a pair of reels between which the ribbon is serially wound, reversible intermittent reeldriving means, and reel-positioning means for guiding the ribbon as it is wound. Separate sensors detect the ribbon edge position adjacent to each reel for controlling the reel-positioning means. Other sensors detect the completion of the winding on either reel, and serve both to reverse the direction of winding, and to select one of the edge-sensors, which is adjacent to the reel that is winding the ribbon at any given time, to control the guiding function. A control circuit includes means for registering momentary actuations of the sensors to control the guiding and feeding operations. Signal generators also act through register means in the control circuit to discontinue ribbon feeding during halts in the operation of an associated printing machine, but permit the intermittent drive to complete a full cycle before disengagement occurs.

llnited States atent n91 Satas et al.

[ RIBBON REWINDING APPARATUS ESPECIALLY FOR HIGH SPEED PRINTERS [75] Inventors: Wallace J. Satas, Hudson; Joseph Konkel, Lynnfield, both of Mass.

[73] Assignee: Data Printer Corporation, Cambridge, Mass.

22 Filed: Sept. 10, 1970 21 Appl. No.; 71,068

[56]. References Cited UNITED STATES PATENTS 3,026,057 3/1962 Horimura ..242/57 X 3,051,405 8/1962 Lyon ....242/57 X 3,511,451 5/1970 Emmert... ....242/57 X 3,542,183 11/1970 Stiffler ..197/l65 May 1,1973

3,584,723 6/1971 Anderson ..l97/l65 Primary Examiner--George F. Mautz Att0rneyRich & Ericson [5 7 ABSTRACT Ribbon rewinding apparatus includes a pair of reels between which the ribbon is serially wound, reversible intermittent reel-driving means, and reel-positioning means for guiding the ribbon as it is wound. Separate sensors detect the ribbon edge position adjacent to each reel for controlling the reel-positioning means. Other sensors detect the completion of the winding on either reel, and serve both to reverse the direction of winding, and to select one of the edge-sensors, which is adjacent to the reel that is winding the ribbon at any given time, to control the guiding function. A control circuit includes means for registering momentaryao tuations of the sensors to control the guiding and feeding operations. Signal generators also act through re- 19 Claims, 11 Drawing Figures PATENTEUW 11m 3,730,449

SHEET 2 BF 5 v VE/VTORS WALLACE J. SATAS JOSEPH KONKEL B ww ATTORNEYS PATENT Y 1 ms SHEET 3 OF 5 rsuo M/VE/VTORS WALLAQE J. SATAS JOSEPH KONKEL I ATTORNEYS TSU/ TSUO

PATENTED H975 $730,449

WALLACE J. SATAS JOSEPH KONKEL A r TORNE rs RIBBON REWINDING APPARATUS ESPECIALLY FOR HIGH SPEED PRINTERS BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION The present invention relates to apparatus for reversibly winding an inked printing ribbon for use in printers, and especially in printers of the high speed impact drum type. Conventionally, such a printer has a print drum on which are engraved a set of the characters that can be printed for each column. The drum is rotated at a constant speed in tangential relation to the printing paper and an inked ribbon, which are backed by a row of hammers arranged in a straight line parallel to the rotational axis of the drum. One hammer is provided for each vertical column to be printed, and cooperates with a corresponding column of different characters around the surface of the drum. Precisely timed actua tion ofa hammer in a given column imprints by striking the paper and ribbon against a selected character on the drum.

Typically, printers of this type may produce 600 lines or more per minute, so that each line is printed in a matter of only 1/10 of a second. In order to produce a uniform weight and quality of print, it is necessary to advance the printing ribbon regularly, to avoid overstriking the same area repeatedly.

The ribbon is conveniently reversibly wound by attaching its ends to a pair of reels. It may be reused a number of times by winding it back and forth between the reels as printing continues. It is, however, necessary to provide some means for guiding the ribbon accurately so that it will wind properly onto the reels, and to prevent it from wandering from side to side. The printing operations are often carried out in an intermittent fashion, with idle intervals during which no data is supplied to the printer. During these idle intervals it is preferred not to advance the printing ribbon. It is therefore desired to interrupt the ribbon-feeding whenever printing operations are not in progress.

It is the general object of the present invention to provide an improved apparatus for rewinding inked printing ribbon in a reversible manner, for guiding the ribbon in a predetermined path as it is wound and rewound, and for continuing the feeding of the ribbon only during periods of printing by an associated printing machine. It is another object to provide a compact and highly reliable apparatus for rewinding printing ribbon. Further objects and advantages of the invention will appear as the following description proceeds.

Briefly stated, according to a preferred embodiment of our invention, we attach the ends ofa length of inked printing ribbon to a pair of reels, and mount these reels on adjustable supporting means which normally hold the reels in parallel relation, so that the ribbon may be threaded through the related printing mechanism from one reel to the other. The reels are driven by reciprocating pawl means cooperating with ratchet means to advance the ribbon in intermittent steps. The direction of winding is selected by sensing means which detect the completion of unwinding of the ribbon from either reel, and serve to reverse the feeding direction of the pawl and ratchet means. 1

The reel-supporting means are movable in a manner to cant the reels relative to the length of the ribbon for purposes of guiding it in a predetermined track. The

guiding function is controlled by a pair of ribbon edgesensing means, one of which is located adjacent to each reel. The end sensing means are arranged to enable either of the two edge-sensing means alternatively, selecting that one of these means which is associated with the reel onto which the ribbon is being wound at any given time. In this manner the winding reel is used to guide the ribbon to form an accurate roll, while the supply reel is allowed to unwind in any fashion dictated by the requirements of guiding onto the winding reel.

The continuance of these winding and guiding operations is subject to the presence ofa signal indicating the continuance of printing operations. Interruption of this signal affects a control circuit in a manner to discontinue feeding of the ribbon. However, the pawl and ratchet means are held in ribbon-feeding engagement after the printing signal ceases for an interval long enough to insure that the ribbon will be advanced one full step. Otherwise, when single lines are being printed at intervals, the printing signal might not endure long enough to allow the pawls to complete a full cycle of reciprocation and thereby engage the ratchet means to advance the ribbon.

DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out the subject matter which we regard as our invention, it is believed that a clearer understanding may be gained from the following detailed description of a preferred embodiments thereof, referring to the accompanying drawings, in which:

FIG. I is a fragmentary view in perspective showing a preferred embodiment of the improved ribbon rewinding apparatus;

FIG. 2 is a fragmentary view in elevation showing a feeding mechanism;

FIG. 3 is a sectional end view showing end sensing means which form a portion of the apparatus;

FIG. 4 is a fragmentary view partially in section showing a portion of the reel mounting and feeding mechanism;

FIG. 5 is a schematic perspective view illustrating the guiding action of the apparatus;

FIG. 6 is a sectional view in elevation showing an edge-sensing means with the parts in a position corresponding to a misaligned position of the ribbon;

FIG. 7 is a fragmentary view of the means of FIG. 6, showing positions of the parts assumed when the ribbo is in the proper track;

FIG. 8 is a view similar to FIG. 7, but showing the parts in positions assumed when the ribbon is misaligned in an opposite sense to FIG. 6;

FIG. 9 is a fragmentary plan view of the means of FIGS. 68;

FIG. 10 is a diagram of a control circuit for the apparatus; and

FIG. 11 is a timing diagram of the control circuit of FIG. 10.

Referring first to FIGS. l-S, a preferred embodiment of the improved rewinding apparatus is organized about a yoke frame which includes end plates 10 which are joined by ribbon guide castings 22. The yoke frame is intended to be pivotally mounted on a printer frame, and is provided with bores 12 for this purpose, as well as arcuate slots 20 which permit the frame to be swung into operative relation to the main frame of the printer (not shown), or swung outwardly for replacement of the ribbon. The guides 22 partially enclose a conventional print drum PR, which is rotatably mounted in the yoke frame and is arranged to be driven at a predetermined rate by means which include sheaves 17 and 18, the latter being mounted on a stub shaft 14, a belt 16 and a suitable motor (not shown). The print roll PR has rows of characters engraved on its surface in a conventional manner for cooperation with the hammers of the printing machine. The ribbon passes tangentially over the surface of the print roll together with the printing paper, so that impact by the printing hammers produces desired images on the paper. As the present invention is not concerned with the printing machine itself, and is useful in conjunction with a variety of conventional printers, no further description of the printing mechanism is believed necessary.

The inked printing ribbon 24 is partially wound on reels 26 and 28, and extends between them about the ribbon guides 22. The reels 26 and 28 are supported at their right ends as seen in FIG. 1 by means of capped shafts 102 and 104, which are resiliently biased by coil springs 110 into engagement with the ends of the reels, for purposes of convenient removal and replacement of the reels when the ribbon is to be replaced. The shafts 102 and 104 are supported in a skew bracket 100, which is pivotable about a bolt 108 that is mounted on the plate at the right side of the yoke frame. The skew bracket 100 may be angularly positioned about the shaft 108 by means of solenoids TSl or T52, which are connected to a link 106 that is slideably engaged with a tongue 107 extending from the skew bracket. By actuating either of the solenoids TSl or TS2 the skew bracket 100 may be canted in a manner to tilt the reels 26 and 28 in opposite angular directions with respect to the longitudinal dimension of the ribbon 24. For example, the reels are shown in FIG. 5 in a tilted position at 26 and 28, while the normal position perpendicular to the length dimension of the ribbon is shown in dashed lines at 26' and 28'. The tilted positions are in this case produced by energizing the solenoid TS2, which tilts the bracket 100 counterclockwise as seen in FIG. 5, shifting the right end of the roll 26 rearwardly and the corresponding end of the reel 28 forwardly. It is a wellestablished principle that a sheet may be guided by tilting the reels in this fashion, since any longitudinal elementor edge of the sheet tends to wind itself in a plane radial to the longitudinal axis of rotation of the reel. Thus, tilting of the reels in the sense shown in FIG. 5, assuming that the ribbon is winding onto the lower reel 28 as shown by the arrow, tends to shift the ribbon toward the left as viewed in FIG. 5. Similarly, ifthe ribbon is being rewound in the opposite direction onto the upper reel 26, the illustrated angle of tilting will tend to shift the ribbon toward the right side of this reel. Conversely, actuation of the solenoid TSl would tilt the bracket 100 in the opposite sense, and guide the ribbon in the opposite directions, according to the direction of winding.

We provide edge sensing means comprising a pair of sensing switches TSU and TSL, which are respectively positioned adjacent to the upper reel 26 and the lower reel 28. We utilize only one of these switches at a time, depending upon the winding direction, as it is desired to guide the ribbon correctly onto the winding reel, while the supply reel may be allowed to unwind without guidance of the ribbon at that location.

One of the edge sensing switches TSU, which is identical with the switch TSL, is shown in detail in FIGS. 6-9. The casing 112 of the switch TSU slideably supports a ribbon sensor 114, having a V-notch 118 in which the edge 25 of the ribbon 24 is slideably received. The sensor is movable within the limits of a slot 1 15 formed in an upper ribbon guide 116 which extends partially over the edge of the ribbon to prevent it accidentally becoming disengaged from the sensor. A pin 120 guides the sensor, which is biased by a compression spring 122 into light contact with the edge 25 of the ribbon. The sensor carries two spaced magnets 124 and 126, which cooperate with pairs of ferromagnetic reed switch contacts TSUO and TSUI, which serve respectively to determine inner and outer tolerance limits of displacement of the edge 25. Assuming that this edge is in a predetermined correct track shown in solid line at 25, the sensor 114 assumes the position shown in FIG. 7, in which the magnets 124 and 126 attract the upper one of each pair of contacts TSUO and TSUI more strongly than the lower one, so that both sets of contacts are held open. In the event that the edge of the ribbon shifts toward the right to a limiting position shown at 25" in FIG. 6, the magnet 124 sufficiently attracts the lower one of the contact pair TSUO to close this pair, but the magnet 126 holds its contact set TSUI in an open condition. Conversely, a leftward shift of the ribbon edge to a position 25 illustrated in FIG. 8, causes the magnet 126 to attract the lower one of the contact pair TSUI enough to close this pair, while the contacts TSUO are held open by the magnet 124. These switches form a portion of a control circuit which will be described hereinafter.

Referring now to FIGS. 1 and 4, the left ends of the reels 26 and 28 are slideably received by drive caps 30, which are rotatably supported by bearings 41 mounted by housings 40 in the plate 10 at the left side of the assembly. Because of the necessity to allow the reels to cant, the left end of each reel is formed with a notch 34 in which a drive pin 32 affixed to the corresponding cap 30 is slideably received. Thus the reels are drivingly connected with the caps, but are nevertheless free to cant with respect to the rotational axes of the caps. Each cap is secured on a shaft 43, and a pair of ratchet wheels 42 and 44 are secured to these shafts outboard of the plate 10. As best shown in FIG. 2, the mechanism for driving the reels alternatively through their ratchets 42 and 44, includes a drive sheave 86 which is secured to a protruding end portion of the print roll PR. A belt 87 is threaded about the sheave 86, an idler sheave 84, and a driven sheave 82, the latter being rotatably supported on an eccentric drive shaft 81. This shaft is provided with an eccentric portion and with a concentric portion mounting a bracket 88 which movably supports the sheave 84 to provide for adjustment of the tension in the belt 87. An adjusting screw 92 is threaded into a stationary support member 93, and extends through an arcuate slide 90 formed in the bracket 88, so that the belt tension may be adjusted by loosening the screw 92 and turning the bracket 88 about the shaft 81.

The eccentric portion 80 of the shaft 81 is engaged rotatably in a hub portion 78 of each of two actuator arms 76. Each of these arms bears a slotted pawl 64 for driving cooperation with the ratchet wheels 42 and 44, respectively. The actuator arms 76 are movable to engage or disengage the pawls 64 with the ratchet wheels 42 or 44 by means of feed solenoids F81 and F82, whose actuating rods 70 are respectively pivotally connected with links 77, which are in turn pivotally supported on the plate by pivotal connections 66. Each of the links 77 rotatably mounts a cam 74, which is in turn slideably received in a slot 79 formed in each of the actuators 76. The actuators are continuously reciprocated in a direction lengthwise of the pawls 64, by the rotation of the eccentric portion 80, and are guided in this sliding motion by the cams 74. Energization of either of the solenoids PS1 or F82 swings the corresponding link 77 toward the related ratchet wheel 42 or 44, and brings the pawl 64 into position to drivingly engage the teeth of that ratchet wheel. In FIG. 2, the solenoid PS2 is assumed to be energized, so that the upper pawl 64 is drivingly engaged with the ratchet 42. A pair of springs 91 attached to the plate 10 bias the links 77 and actuators 76 away from the ratchet wheels 42 and 44, so that de-energization of either solenoid permits the pawl 64 to be drawn away from engagement with the corresponding ratchet wheel. It is assumed in FIG. Z that the solenoid PS1 is de-energized, and the lower pawl 64 is shown disengaged from its ratchet wheel 44.

The pawls 64 reciprocate once on each complete revolution of the eccentric portion 80 and the sheave 82, and advance the driven ribbon reel through an arc corresponding to one ratchet tooth during this revolution. The rate of advance of the ribbon is correlated with the rate of rotation of the print drum by proper selection of the speed ratio between the sheaves 86 and 82. In the illustrated embodiment, this ratio is selected at 3:1, so that the pawls 64 reciprocate through one full stroke in the course of three revolutions of the print roll. The control circuit, which will be described thereinafter, is so arranged that upon a cessation of printing operations, the feeding of the winding reel is continued through one full stroke of the actuators 76.

As shown in FIGS. 1, 3 and 4, back tension is maintained in the ribbon by means of belts 38 trained about cylindrical surfaces 36 of the caps 30. One end of each belt is affixed to a stationary mounting block 58, and the opposite ends are connected by a tension spring 39. These belts apply braking friction to either of the reels 26 or 28 which is serving as the supply reel at any given time.

Means are provided for detecting the completion of unwinding of the ribbon from either of the reels 26 and 28, and these are illustrated in FIGS. 1 and 3. A pair of metal strips 54 are secured near each end of the ribbon, and are sufficiently long to extend slightly out from the edges. These strips cooperate with jaws 52 formed in a pair of reversing levers 48, which are pivotally supported at pivot points 49 on the mounting block 58. This block is supported near the left end of the assembly, and positions the jaws 52 closely adjacent to the reels and their caps 30, each in a position to be engaged by a corresponding one of the strips 54 as the ribbon becomes fully unwound from the adjacent reel.

This engagement pivots the corresponding lever 48 in a direction to withdraw a magnet 56 mounted thereon away from an associated end-sensing switch UES or LES. These switches are normally closed by internal magnets (not shown), but in the juxtapositions shown, the magnets 56 hold these switches in open condition. As either holding magnet 56 is raised by its lever 48, the corresponding switch UES or LES is permitted to close under the influence of its internal magnet. These switches serve to reverse the direction of ribbon feeding, and are incorporated in a control circuit which is now to be described.

THE CONTROL CIRCUIT The functions of the control circuit are: first, to cause the ribbon to feed between the upper and lower reels, and to reverse the feeding when the ribbon is fully wound on either reel; secondly, to guide one edge of the ribbon in a predetermined track in order to cause it to wind properly on the reels, in either winding direction; and thirdly, to interrupt the feeding of the ribbon when printing operations stop, after an interval long enough to complete a full stroke of the ribbon drive pawls.

The circuit shown in FIG. 10 includes five conventional integrated flipflop circuits or register means F 1 through F5 inclusive, each of which has a set terminal S, a reset terminal R, and output terminals 1 and 0. The flip-flops F1 and F2 are also provided with direct set terminals'DS, direct reset terminals DR, and trigger terminals C. Both flip-flops F1 and F2 are so arranged that they can be set, i.e., so that their output terminals 1 will deliver a logic 1 signal, either by applying a logic 1 signal to a terminal DS, or by applying a triggering pulse to terminal C while a logic 1 signal is applied to terminal S. These flip-flops can be reset, i.e., so that their output terminals 0 will deliver a logic 1 signal, by applying a logic 1 signal to terminal DR, or by applying a triggering pulse to terminal C while a logic 1 signal is applied to terminal R. As will be understood by those skilled in the art, the logic 1 signal must be present at the terminal S or R for a short time prior to the trigger pulse in order to be effective. Both terminals C are connected to a conventional index pulse generator 1C, which is energized momentarily at the completion of each revolution of the print roll PR to apply a triggering pulse transition to the terminals C of the flip-flops F1 and F2. Inverters I apply logic I signals to the reset terminals R when activated by logic 0 signals.

The terminal 0 of the flip-flop F1 and the terminal 1 of flip-flop F2 are respectively connected to the terminals A and B of a NOR gate G1, whose output terminal C serves to inhibit ribbon feeding after printing operations are interrupted. The flip-flops F1 and F2 have their direct set terminals DS connected in common to a conventional print signal generator PS. The signal generator PS produces a signal PS so that while printing operations continue, both flip-flops F1 and F2 remain set, as shown during the interval 0-1 in the time diagram of FIG. 1 1.

During this printing period, index pulses IC are generated at the completion of each revolution of the print roll PR, and are applied to the terminal C of the flip-flop Fl, but do not change its set condition even though the reset terminal R continually receives a logic 1 signal from its inverter I and the terminal of the flipflop F2; the brief index pulse 1C is ineffective to overcome the printing signal at the direct set terminal DS. Not until the printing signal PS ceases can an index signal succeed in resetting the flip-flop F1, as shown at time 2 in FIG. 11.

During the printing period between times 0 and l, the terminal 0 of the flip-flop F1 delivers a logic 0 signal, and the terminal 1 of the flip-flop F2 delivers a logic 1 signal, to the NOR gate G1, whose output terminal C therefore delivers a logic 0 signal. This gate is connected to the terminals A of each of two NOR gates G2 and G3, which control ribbon feeding. Either of these gates is therefore incipiently prepared to transmit logic 1 signals from its output terminal C at this time, provided that it also receives a logic 0 signal at its terminal B.

The direction of ribbon feeding is determined by the last previous momentary closing of one of the ribbon and switches UES or LES by the engagement of one of the strips 54, previously described, with its cooperating switch lever 48. A voltage source B1 is normally applied to the terminals S and R of the flip-flop circuit or register means F3 through resistors R1 and R2 respectively, but either terminal can be grounded and supplied with a logic 0 signal by closing a corresponding one of the switches UES or LES. In the event that the upper ribbon end switches UES is closed by the exhaustion of ribbon from the upper ribbon reel 26, for example, this momentarily grounds the terminal S to set the flip-flop F3. The flip-flops F3, F4, and F5 are of a type which can be set or reset by logic 0 signals. The flip-flop F3 remains in a set condition until such time as the lower ribbon end switch LES is close by exhaustion of the ribbon from the lower reel 28; this in turn momentarily grounds the reset terminal R and resets the flip-flop F3.

Assuming a set condition of the flip-flop F3, the ribbon having been exhausted from the upper reel 26, a logic 1 signal is applied to the terminal B of the gate G2, inhibiting this gate and producing a logic 0 signal at its terminal C. The lower ribbon feed solenoid PS1 is de-energized at this time, as a controlling electronic switch S1 is in an open condition. However, the terminal 0 of the flip-flop F3 delivers a logic 0 signal to the terminal 8 of the gate G3, resulting in the delivery ofa logic 1 signal from the terminal C of this gate to an electronic switch $2. This in turn energizes the upper ribbon feed solenoid FS2 from a power source B2. The solenoid FS2 engages its feed pawl 64 with the upper ribbon reel ratchet 42, and commences rewinding of the ribbon on the upper reel.

A reversal of the direction of feeding occurs when the supply of ribbon becomes exhausted from the lower reel 28 and its end strip 54 contacts the switch LES. This momentarily grounds the terminal R of the Hip flop F3, which is thereby reset, and applies a logic 1 signal to the terminal B of the gate G3 to inhibit this gate. The switch S2 then opens and de-energizes the upper ribbon feed solenoid FS2, discontinuing the feeding of ribbon onto the upper reel 26. At the same time, terminal 1 of the flip-flop F3 applies a logic 0 signal to terminal B of the gate G2, causing this gate to deliver a logic 1 signal and thereby energize the switch S1 and the lower ribbon feed solenoid FSl. This engages the lower ribbon feed pawl 64 with the lower reel ratchet 44, and the ribbon is subsequently re-wound from the upper reel onto the lower. Rectifiers R are provided to protect the electronic switches S1 and S2 from excessive voltages when either of the switches 81 or S2 is opened.

It will be seen that the logic circuit is so arranged that the switches UES and LES control the periodic reversal of the direction of ribbon feeding, while the print signal generator PS permits feeding to continue so long as printing operations are taking place. In the event that printing is stopped, feeding is continued through one full revolution of the pawldriving shaft 81, which corresponds to three revolutions of the print roll PR. This insures that the engaged feed pawl completes a full stroke before it is disengaged from the teeth of the corresponding ribbon reel ratchet 42 or 44. Referring to the time diagram of FIG. 11, in conjunction with FIG. 10, it is assumed that the printing signal P5 is discontinued at time 1. Upon the occurrence of the next succeeding index pulse IC at time 2, the flip-flop Fl, no longer held by the printing signal, is reset by the simultaneous receipt of the index pulse and of a logic 1 signal at terminal R, the latter being delivered continuously by the inverter I from the terminal 0 of the still-set flipflop F2.

The resetting of F1 does not reset F2 at this moment, because the logic 0 signal now delivered by the terminal 1 of F1, applying a resetting signal through an inverter I to the terminal R of F2, does not become effective until the trigger pulse is gone. However, upon the delivery of the next index pulse IC at time 3, the logic 1 signals simultaneously applied to the terminals R and C of the flip-flop F2 are effective to reset it.

When the third index pulse IC following the cessation of the print signal PS is delivered at time 4, it is effective to set the flip-flop Fl, acting in conjunction with the logic 1 signal received at the terminal S of F1 from terminal 0 of the reset flip-flop F2.

Thus at time 4 F1 is set and F2 is reset, with the result that the terminal 0 of F1 applies a logic 0 signal to gate G1, while the terminal 1 of F2 also applies a logic 0 signal to this gate. Terminal C of the gate G1 then delivers a feed-inhibiting logic 1 signal to the terminals A of gates G2 and G3 for the first time. This results in the opening of either switches S1 or S2, (depending on the state of F2) disengaging the ribbon feed solenoid PS1 or PS2 and causing the ribbon feeding to stop. It is to be noted that the logic signals applied to terminals A and B of the gate G1 during the time interval 0-2 are 0,1; during the time interval 2-3 are 1,1; and during the interval 3-4 are 1,0. None of these combinations results in the delivery of an inhibiting logic 1 signal to the gates G2 and G3, so that only at time 4, when F2 is reset and F1 is set, does the ribbon feeding stop.

The purpose of continuing the ribbon feeding after the print signal ceases is to insure that the ribbon will not remain stationary when single lines are being printed at intervals. A print signal lasting through only one or two revolutions of the print roll is too brief for the completion of one revolution of the shaft 81 and a full cycle of reciprocation of the feed pawls, which might therefore not fully engage the ratchet wheels and advance the ribbon. Continuing the pawl engagement until three index pulses are generated guarantees that the pawls will complete a full cycle and advance the ribbon.

During the time interval 4-5, index pulses IC attempt to set the flip-flop F2, in concert with the logic 1 signal received at the terminal S of this flip-flop; but they are prevented from doing so by the logic 1 signal delivered by terminal to the direct reset terminal DR.

It is assumed in FIG. 11 that printing is resumed at some later time 5. The receipt ofa renewed print signal at the terminal DS sets the flip-flop F2, which now delivers a logic 1 signal to the gate G1. This gate then produces a logic 0 signal at its terminal C, removing the previous feed-inhibitinglogic 1 signal from the terminals A of the gates G2 and G3. Feeding of the ribbon then resumes, under the directional control of the switches UES and LES.

Guiding of the ribbon is controlled by that one of the upper and lower edgetracking sensors TSU and TSL which is associatedwith the ribbon reel onto which the ribbon is winding at any given time. The terminals S and R of both of the flip-flops or register means F4 and F are connected through resistors R3-R6 to the voltage source B1. The upper edge-tracking switches TSUO and TSUI are respectively operable, when either of them is closed by lateral displacement of the edge of the ribbon to one of its tolerance limits, to ground a corresponding terminal S or R and thereby set or reset the flip-flop circuit F4. Similarly, the lower edgetracking switches TSLO and TSLI are respectively operable, when either is closed, to ground a corresponding terminal S or R and thereby set or reset the flip-flop circuit F5.

The output terminals of the flip-flops F4 and F5 are connected respectively to the input terminals B of NAND gates G4 and G5, whose output terminals C exhibit a logic 1 signal under all conditions other than receipt of logic 1 signals at both input terminals. The state of terminal B of either gate G4 or G5 will depend upon the last previous actuation of the corresponding edge-tracking switch TSU or TSL, respectively, by displacements of the ribbon edge.

The input terminals A of gates G4 and G5 are connected respectively to the terminals 1 and 0 of the flipflop circuit F3, and consequently only one of them receives a logic 0 signal at any given time; this will be at gate G4 while the ribbon is winding onto the lower reel 28 after actuating the lower end switch LES, and at gate G5 while the upper reel 26 is being rewound after actuation of the upper end switch UES. Therefore, terminal C of the NAND gate G4 must exhibit a logic 1 signal whenever the ribbon is winding onto the lower reel, regardless ofthe logic signal issued by the flip-flop F4 and the upper tracking switches TSUO and TSU], and these switches are rendered ineffective to control the guiding function. Similarly, terminal C of the NAND gate G5 must exhibit a logic 1 signal whenever the ribbon is winding onto the upper reel, and the signals then produced by the lower tracking switches TSLO and TSLl become ineffective to control ribbon guiding. In this manner, the ribbon-end switches UES and LES select the upper or lower tracking switches in accordance with the winding direction, that set of tracking switches which is associated with the winding reel being chosen.

The terminals C of gates G4 and G5 are respectively connected to the input terminals A and B of a third NAND gate G6, whose output terminal C delivers a logic 1 signal under all conditions other than receipt of logic 1 signals at both input terminals. Assuming that the ribbon is winding onto the upper reel, terminal B of the gate G6 continually receives a logic 1 signal from the gate G5. Gate G4 and terminal A of the gate G6 will therefore determine the output of the latter gate, which will be a logic 0 signal if the upper tracking switch TSUO was last actuated, or a logic 1 signal if the upper tracking switch TSUI was most recently closed.

A logic 0 output from the gate G6 actuates an electronic switch S4 through an inverter 1, to energize the lower tracking solenoid TSl from a voltage source B3; this rocks the reel-supporting bracket downwardly, tilting the rolls in a manner to guide the controlling ribbon edge laterally outwardly, opposite to the displacement that closed the switch TSUO. Conversely, a logic 1 output from the gate G6 actuates an electronic switch S3 to energize the upper tracking solenoid T82, and rock the bracket 100 upwardly, thereby guiding the controlling ribbon edge laterally inwardly. This guiding action periodically reverses so long as the ribbon is winding onto the upper reel.

As the ribbon becomes fully wound on the upper reel and the feeding is reversed in favor of the lower reel 28, terminal A of the gate G6 begins to receive a continuous logic 1 signal from the gate G4, and the upper tracking switches give up control of the guiding function to the lower tracking switches TSLI and TSLO, which thereafter control the signals delivered to terminal B of the gate G6 through the gate G5. The output of gate G6 will then be a logic 0 signal if the tracking switch TSLI was last actuated, or a logic 1 signal if the tracking switch TSLO was most recently closed. A logic 0 output again actuates the lower tracking solenoid TSl, tilting the bracket downwardly and guiding the controlling ribbon edge laterally inwardly; while a logic 1 output raises the bracket by actuating the solenoid T82, and guides the controlling ribbon edge laterally outwardly. The guiding action reverses at each successive actuation of one of the lower tracking switches, until the ribbon is fully wound on the lower reel and the cycle is reversed.

What we claim is:

1. In a high-speed printer, apparatus for rewinding an inked printing ribbon of definite length, comprising:

a pair of reels adapted for winding the ribbon reversibly from one to the other; means for reversibly driving said reels to wind and rewind the ribbon thereon; means for adjustably positioning said reels for guiding the ribbon;

end-sensing means for detecting the completion of winding of the ribbon on either of said reels and adapted to provide a signal when the winding of the ribbon on either reel has been substantially completed;

edge-sensing means for detecting the position of an edge of the ribbon at each of two locations adjacent to each of said reels, and adapted to provide a signal when the position of said edge of the ribbon varies from a predetermined path;

andcontrol circuit means electrically connected with said end-sensing means and said edge-sensing means;

said control circuit means including means to receive a signal from said end-sensing means at the completion of winding of the ribbon on either of said reels, means to reverse the direction of winding of the ribbon by said reversible driving means on said reels upon receipt of a signal from said end-sensing means,

position-control means connected to receive said signals from said edge-sensing means and responsive thereto to provide control signals to said positioning means to maintain the ribbon in its predetermined path,

said reverse winding means producing output signals in response to signals received from said endsensing means,

and means connected to said reverse winding means to receive said output signals therefrom and responsive thereto to inhibit response of said position-control means to that one of said edge-sensing means which is adjacent to that one of said reels from which the ribbon is being unwound at any time, while enabling the other of said edge-sensing means to control said positioning means through said position-control means.

2. Apparatus as recited in claim 1, in which said endsensing means comprise a pair of momentary contact switches each selectively actuable by the approach thereto ofa different end of the ribbon.

3. Apparatus as recited in claim 1, there being a pair of said edge-sensing means, each comprising magnetic means movable by an edge of the ribbon, and a pair of magnetically-actuable switches, a different one of said switches being actuable by a displacement of an edge of the ribbon and said magnetic means in each lateral direction.

4. Apparatus as recited in claim 1,

said edge-sensing means including means for detecting a deviation of an edge of the ribbon of predetermined magnitude in either lateral direction;

said means to provide signals to said positioning means comprising register means connected with said edge-sensing means to register the direction of the last previous lateral deviation detected thereby,

said register means being operatively connected to adjust said positioning means to guide the ribbon in the lateral direction opposite to the direction of said last previous deviation.

5. Apparatus as recited in claim 1,

said end-sensing means comprising a pair of switches selectively actuable by momentary contact, and each actuable by the approach ofa corresponding end of the ribbon as that end is unwound from a corresponding reel.

6. Apparatus as recited in claim 5,

said end-sensing means further including pivotally mounted levers engageable by means affixed adjacent to the ends of the ribbon to actuate said switches.

7. Apparatus as recited in claim 1, there being a pair of said edge-sensing means, each comprising a pair of switches, a different one of said switches being actuable by a displacement of an edge of the ribbon in each lateral direction.

8. Apparatus as recited in claim 7, each of said edgesensing means further comprising:

magnetic means movable by an edge of the ribbon, a

different one of said pair of switches being magnetically actuable by a displacement of said magnetic means in each lateral direction.

9. Apparatus as recited in claim 1,

said reverse winding means being constructed and arranged to drive said reels intermittently and to advance said reels through steps of predetermined arc.

10. Apparatus as recited in claim 9, in which said reversible driving means comprise a pair of ratchet wheels each drivingly connected with one of said reels,

a pair of pawl means for cooperation each with one of said ratchet wheels,

means constructed and arranged to reciprocate each of said pawl means relative to a corresponding one of said ratchet wheels, and

means operable by said control circuit means for selectively engaging either of the pawl means with the corresponding one of said ratchet wheels to advance a selected one of said reels.

1 1. Apparatus as recited in claim 10,

said reciprocating means comprising a pair of reciprocably-and pivotally-supported arms, each bearing one of said pawl means,

and drive means constructed and arranged for reciprocating said arms;

said engaging means being constructed and arranged to selectively pivot either of said arms to a position engaging pawl means borne thereby with a corresponding one of said ratchet wheels; together with means pivotally biasing said arms in directions to disengage said pawl means from said ratchet wheel.

12. Apparatus as recited in claim 11,

said drive means comprising rotatable eccentric means engaged with said arms, and means for continuously rotating said eccentric means to reciprocate said arms.

13. Apparatus as recited in claim 1, said means for adjustably positioning said reels comprising a pivotally-mounted bracket supporting one end of each of said reels, and

means for tilting said bracket about its pivotal mounting to cant said wheels relative to the longitudinal dimension of the ribbon to guide the ribbon.

14. In a high-speed printer, apparatus for rewinding an inked printing ribbon of definite length, comprising:

a pair of reels adapted for winding the ribbon reversibly from one to the other; means for reversibly driving said reels to wind and rewind the ribbon thereon; means for adjustably positioning said reels for guiding the ribbon;

edge-sensing means for detecting the position of an edge of the ribbon at each of two locations adjacent to each of said reels, and adapted to provide guiding signals when the position of said edge of the ribbon varies from a predetermined path;

and control circuit means electrically connected with said edge-sensing means, said control circuit means including;

means to reverse said driving means periodically to wind and rewind the ribbon,

means to provide reverse signals when the winding direction of the ribbon is reversed,

pair of said edge-sensing means, each comprising a pair of switches, a different one of said switches being actuable by a displacement of an edge of the ribbon in each lateral direction.

position-control means connected to receive said guiding signals from said edge-sensing means and responsive thereto to provide control signals to said positioning means to maintain the ribbon in its predetermined path,

and means connected to receive said reverse signals and responsive thereto to inhibit response of said position-control means to that one of said edgesensing means which is adjacent to that one of said reels from which the ribbon is being unwound at any time, while enabling the other of said edgesensing means to control said positioning means through said position-control means.

15. Apparatus as recited in claim 14, there being a 16. Apparatus as recited in claim 15, each of said edge-sensing means further comprising:

17. Apparatus asrecited in claim 16, each of said edge-sensing means further comprising:

bon of predetermined magnitude in either lateral direction;

said control circuit means including register means connected with said edge-sensing means to register the direction of the last previous lateral deviation detected thereby,

said register means being operatively connected to adjust said positioning means to guide the ribbon in the lateral direction opposite to the direction of said last previous deviation.

19. Apparatus as recited in claim 14, said means for adjustably positioning said reels comprising:

a pivotally-mounted bracket supporting one end of each of said reels, and

means for tilting said bracket about its pivotal mounting to cant said wheels relative to the iongitudinal dimension of the ribbon to guide theribbon. 

1. In a high-speed printer, apparatus for rewinding an inked printing ribbon of definite length, comprising: a pair of reels adapted for winding the ribbon reversibly from one to the other; means for reversibly driving said reels to wind and rewind the ribbon thereon; means for adjustably positioning said reels for guiding the ribbon; end-sensing means for detecting the completion of winding of the ribbon on either of said reels and adapted to provide a signal when the winding of the ribbon on either reel has been substantially completed; edge-sensing means for detecting the position of an edge of the ribbon at each of two locations adjacent to each of said reels, and adapted to provide a sIgnal when the position of said edge of the ribbon varies from a predetermined path; and control circuit means electrically connected with said endsensing means and said edge-sensing means; said control circuit means including means to receive a signal from said end-sensing means at the completion of winding of the ribbon on either of said reels, means to reverse the direction of winding of the ribbon by said reversible driving means on said reels upon receipt of a signal from said end-sensing means, position-control means connected to receive said signals from said edge-sensing means and responsive thereto to provide control signals to said positioning means to maintain the ribbon in its predetermined path, said reverse winding means producing output signals in response to signals received from said end-sensing means, and means connected to said reverse winding means to receive said output signals therefrom and responsive thereto to inhibit response of said position-control means to that one of said edge-sensing means which is adjacent to that one of said reels from which the ribbon is being unwound at any time, while enabling the other of said edge-sensing means to control said positioning means through said position-control means.
 2. Apparatus as recited in claim 1, in which said end-sensing means comprise a pair of momentary contact switches each selectively actuable by the approach thereto of a different end of the ribbon.
 3. Apparatus as recited in claim 1, there being a pair of said edge-sensing means, each comprising magnetic means movable by an edge of the ribbon, and a pair of magnetically-actuable switches, a different one of said switches being actuable by a displacement of an edge of the ribbon and said magnetic means in each lateral direction.
 4. Apparatus as recited in claim 1, said edge-sensing means including means for detecting a deviation of an edge of the ribbon of predetermined magnitude in either lateral direction; said means to provide signals to said positioning means comprising register means connected with said edge-sensing means to register the direction of the last previous lateral deviation detected thereby, said register means being operatively connected to adjust said positioning means to guide the ribbon in the lateral direction opposite to the direction of said last previous deviation.
 5. Apparatus as recited in claim 1, said end-sensing means comprising a pair of switches selectively actuable by momentary contact, and each actuable by the approach of a corresponding end of the ribbon as that end is unwound from a corresponding reel.
 6. Apparatus as recited in claim 5, said end-sensing means further including pivotally mounted levers engageable by means affixed adjacent to the ends of the ribbon to actuate said switches.
 7. Apparatus as recited in claim 1, there being a pair of said edge-sensing means, each comprising a pair of switches, a different one of said switches being actuable by a displacement of an edge of the ribbon in each lateral direction.
 8. Apparatus as recited in claim 7, each of said edge-sensing means further comprising: magnetic means movable by an edge of the ribbon, a different one of said pair of switches being magnetically actuable by a displacement of said magnetic means in each lateral direction.
 9. Apparatus as recited in claim 1, said reverse winding means being constructed and arranged to drive said reels intermittently and to advance said reels through steps of predetermined arc.
 10. Apparatus as recited in claim 9, in which said reversible driving means comprise a pair of ratchet wheels each drivingly connected with one of said reels, a pair of pawl means for cooperation each with one of said ratchet wheels, means constructed and arranged to reciprocate each of said pawl means relative to a corresponding one of said ratchet wheels, and means operable by said control circuit means for selectively engaging eIther of the pawl means with the corresponding one of said ratchet wheels to advance a selected one of said reels.
 11. Apparatus as recited in claim 10, said reciprocating means comprising a pair of reciprocably-and pivotally-supported arms, each bearing one of said pawl means, and drive means constructed and arranged for reciprocating said arms; said engaging means being constructed and arranged to selectively pivot either of said arms to a position engaging pawl means borne thereby with a corresponding one of said ratchet wheels; together with means pivotally biasing said arms in directions to disengage said pawl means from said ratchet wheel.
 12. Apparatus as recited in claim 11, said drive means comprising rotatable eccentric means engaged with said arms, and means for continuously rotating said eccentric means to reciprocate said arms.
 13. Apparatus as recited in claim 1, said means for adjustably positioning said reels comprising a pivotally-mounted bracket supporting one end of each of said reels, and means for tilting said bracket about its pivotal mounting to cant said wheels relative to the longitudinal dimension of the ribbon to guide the ribbon.
 14. In a high-speed printer, apparatus for rewinding an inked printing ribbon of definite length, comprising: a pair of reels adapted for winding the ribbon reversibly from one to the other; means for reversibly driving said reels to wind and rewind the ribbon thereon; means for adjustably positioning said reels for guiding the ribbon; edge-sensing means for detecting the position of an edge of the ribbon at each of two locations adjacent to each of said reels, and adapted to provide guiding signals when the position of said edge of the ribbon varies from a predetermined path; and control circuit means electrically connected with said edge-sensing means, said control circuit means including; means to reverse said driving means periodically to wind and rewind the ribbon, means to provide reverse signals when the winding direction of the ribbon is reversed, position-control means connected to receive said guiding signals from said edge-sensing means and responsive thereto to provide control signals to said positioning means to maintain the ribbon in its predetermined path, and means connected to receive said reverse signals and responsive thereto to inhibit response of said position-control means to that one of said edge-sensing means which is adjacent to that one of said reels from which the ribbon is being unwound at any time, while enabling the other of said edge-sensing means to control said positioning means through said position-control means.
 15. Apparatus as recited in claim 14, there being a pair of said edge-sensing means, each comprising a pair of switches, a different one of said switches being actuable by a displacement of an edge of the ribbon in each lateral direction.
 16. Apparatus as recited in claim 15, each of said edge-sensing means further comprising: magnetic means movable by an edge of the ribbon, a different one of said pair of switches being magnetically actuable by a displacement of said magnetic means in each lateral direction.
 17. Apparatus as recited in claim 16, each of said edge-sensing means further comprising: a slide bearing said magnetic means and biasing means urging said slide into engagement with an edge of the ribbon.
 18. Apparatus as recited in claim 14, said edge-sensing means being constructed and arranged to detect a deviation of an edge of the ribbon of predetermined magnitude in either lateral direction; said control circuit means including register means connected with said edge-sensing means to register the direction of the last previous lateral deviation detected thereby, said register means being operatively connected to adjust said positioning means to guide the ribbon in the lateral direction opposite to the direction of said last previous deviation.
 19. Apparatus as recited in claim 14, said means for adjustably positioning said reels comprising: a pivotally-mounted bracket supporting one end of each of said reels, and means for tilting said bracket about its pivotal mounting to cant said wheels relative to the longitudinal dimension of the ribbon to guide the ribbon. 